Underfeed furnace



July 2, 1935.

1. A. TAYLOR 2,007,028

UNDERFEED FURNACE Filed Sept. 24, 1931 2 Sheets-Sheet l INVENTOR [RY/Na A. TAYLOR ATTORNEY I July 2, 1935. 0 A. TAYLOR UNDERFEED FURNACE Filed Sept. 24, 1931 2 Sheets-Sheet 2 INVENTOR fzgyma A. Z'QYLOR W & k i

ATTORNEY Patented July 2, 1935 UNITED STATES UNDERFEED FURNACE Irving A. Taylor, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Application September 24, 1931, Serial No. 564,337

4 Claims. (01. 122-4) This invention relates to underfeed furnaces, and more particularly to furnaces of the multiple retort underfeed type which comprise a series of spaced parallel retorts and rows of air admitting g tuyre blocks between the retorts. V

In furnaces of this type the fuel is usually delivered into thefront ends of the retorts by means of reciprocating rams, and the incombustible residues are deposited in a transverse ash 1o dump located in the rear of .the retorts. It is customary to operate such furnaces at high combustion rates which result in high temperatures in the fuel bed, and the air for combustion is frequently preheated prior to its introduction into the air chamber beneath the retorts. Considerable difiiculty has been experienced in construct: ing afurnace which would operate satisfactorily under these conditions, since the tuyre blocks and other heat-exposed partsoften have a comparatively short life of usefulness. p

It is accordingly the main object of .the invention to overcome these difficulties and to provide an underfeed furnace which can be operated continuously at high combustion rates without damage to the various fuelsupporting members.

It is a further object of the invention to provide a multiple retort underfeed furnacewhich is soconstructed that all heat exposed portions thereof areadequately cooled, and overheating of 30 such portions is prevented.

It is a further object of the invention to provide a simple and effective arrangement whereby a suitable cooling fluid such as water may be utilized to absorb heat. from the heat exposed portions of a multiple retort furnace and thus maintain these portions at a relatively low temperature.

It is a further object to :providea multiple retort underfeed furnaceiwhich'isso arranged in connection with a steam boiler that heat may be transferred from the various stoker parts to the water of the boiler, thus cooling the parts and generating steam which mingles with the steam generated in the boiler itself. I

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in thecombinationof parts set forth in the specification and covered by the claims appended hereto. p

Referring to the drawings illustrating one embodiment of the invention, and inwhich like reference numerals indicate like parts, I p

Fig, 1 is a longitudinalsection through an underfeed furnace associated with a steam boiler, :a, portion only of the boiler being shown;

must pass as it leaves the retorts.

Fig. 21s a section on the line 22 of Fig. 1, showing the construction of the stoker. between adjacent parallel retorts; and

Fig. 3 is a section on the line 3--3 of Fig. 2.

The embodiment illustrated in the drawings comprises a furnace chamber l8 above which is mounted a steam boiler having an upperv drum ll anda lower drum l2. These drums are connected'by a bank of steam generating tubes I4. The drum ii is located above the front wall I5 10 of the furnace chamber, and the drum 12 is located above the rear wall I6.

In; order to burn fuel within the furnace chamber and thus liberate heat for the'gene'ration of steam, V I provide a multiple retort underfeed stoker. This stoker comprises a fuel hopper l8 of suitable construction which is mounted outside of and adjacent to the front wall I5of the furnace. A plurality of horizontal cylindrical ram casings it? are mounted beneath thev hopper 20 and arranged to receive fuel therefrom;' vA ram 2!! is mounted within each ram casing anda' suitable gear reduction mechanism 22 is provided to reciprocate the rams and thus deliver fuel to the furnace. 25

A plurality of parallel underfeed retorts 23 extend rearwardly from the front wall. l5, each retort being formed by a bottom plate 24 and two upright side plates 26. The retorts preferably slope downwardly toward the rearjand their rear ends are supported on a transverse beam 21. In' order to move the fuelin. the retortsrearwardly I provide a number of.hori'zontallyl 're ciprocable pusher blocks28 which extend through openings in the retort bottoms 24. Each group of pusher blocks is reciprocated by means of rods 3!! connected to an oscillating lever 3|. Each lever 3| is in turn driven from itscorresponding ram 2!! by means of a rod 32 and a suitable adjustable connecting lever 33. I V 40 The space beneath the'retorts 23 is enclosed to provide an air chamber 35 into: which air maybe delivered under pressure by means of a duct36 from a suitable fan (not shown). A damper 31' may be provided inthe duct to control the rate of flow. -The chamber 35 is closed at the front by a vertical plate 39. The rods 32 extend through op enings'in this plate, andleakage of air past the rods is prevented by fiexibleseals 4U.

At the rear ends of the retorts 23 I preferably provide an overfeed grate 4|, over which the fuel The air supply to the grate ll is controlled by a damper 42 which may be manually adjusted by means of an operating linkage 43. Y.

The space between the overfeed grates 4| and the rear furnace walls l6 constitutes an ash dump or clinker pit 45 into which the incornbustible residues from the fuel are deposited. This pit is preferably of considerable depth so that the ashes will have an opportunity to cool appreciably before leaving the furnace. Furthermore the deep body of ashes forms an efiective seal to prevent air leakage into the furnace. At the bottom of the pit I have shown a rotatable clinker grinder roll 45 and two pivotally mounted plates 41. Each of these plates may be adjusted relative to the roll 46 by means of manually operable linkages 48. Sheet metal seals 50 may be provided to prevent leakage of air into the pit 45. An ash hopper 5| is shown beneath the grinder roll 46 to receive the ashes which are discharged from the pit.

As shown in Fig. 2, the side plates 26 of adjacent retorts are spaced apart to form a passage 53 through which the air for combustion may flow upwardly to the fuel bed. The lines 54 indicate the centers of the retorts.

In order to support the fuel bed above the passage 53 and. properly distribute the air which is supplied to burn the fuel, I provide a tuyere structure which is protected against overheating by means of a suitable cooling fluid such as water. In the embodiment illustrated this tuyre structure comprises a pair of spaced parallel water tubes 55 mounted above the passage 53 and slopping downwardly from front to rear of the furnace in a plane parallel to the top edges of the retort sides 26.

In order to provide an adequate supply of water for the tubes 55 I have shown their rear ends bent downwardly at the rear ends of the retorts and connected to a horizontal header 10, which may be conveniently supported from the beam 21. Water is delivered to the header Ill by means of down-comer tubes 1| leading from the rear boiler drum I2 and preferably extending outside the side walls of the furnace chamber to avoid obstructing the clinker pit 45. The front ends of the tubes 55 extend through the front wall |5 of the furnace and connect to a horizontal header 12, which in turn is connected to the front boiler drum I I by means of up-comer tubes 14. These tubes 14 are preferably arranged to form a water wall which will absorb radiant heat from the furnace chamber, and their lower portions may be protected by means of cast iron blocks 15. Since the exposed water wall tubes 14 will generate steam very rapidly, the down-comers H and the tubes 55 may not supply them with sufficient water. It is therefore desirable to provide a row of downcomer tubes 16 located outside the front wall [5 and connecting the drum II with the header 12. These down-comers ensure an adequate supply of water for the water wall tubes 14.

It will be seen that the rear portions of the tubes 55 form the front wall of the clinker pit 45 and thus absorb heat from the mass of clinkers as they move downwardly toward the grinder roll 46. The spaces between these portions of the tubes may be bridged by blocks 18 of cast iron or other suitable material. The rear wall l6 of the furnace is preferably protected by vertical water tubes 19 connected at their lower ends to a lower horizontal header and at their upper ends to the boiler drum l2. A row of down-comer tubes 8| supplies water from the drum I2 to the header 80. The lower portions of the water wall tubes 'may be protected by means of cast iron blocks 82.

Beneath each pair of tubes 55 is a row of tuyere blocks 9| which are shaped to fit closely against the lower surfaces of the tubes. Each block 9| has a pair of depending vertical plate portions 92 which are fastened to the retort sides 26 by means of screws 94. The plates 92 have tuyere openings leading to the retorts. The blocks 9| are provided with air passages 96 which direct air upwardly and rearwardly between the tubes 90. These tubes not only absorb heat from the blocks 9i, but also protect them to a large extent from contact with the fuel bed. Since the tubes 55 are exposed on their upper surfaces to abrasion from the fuel, they are preferably formed with comparatively heavy walls.

The operation of the invention will now be clear from the above disclosure. Fuel is delivered from the hopper l8 into the retorts 23 by means of the reciprocating rams 20, and the pusher blocks 28 move the fuel rearwardly and upwardly. The top surface of the fuel bed is maintained considerably above the tops of the tubes 55. Air for combustion passes to the fuel from the air chamber 35 through the passages 53 and tuyere openings 95 and 96. Combustion of the fuel is completed'as it passes over the overfeed grates 4|, and the ash is deposited in the pit 45, where it is cooled by the water tubes 19- and 55. The grinder roll 45 is actuated when necessary to prevent an excessive accumulation of ashes and clinkers.

Water circulates rapidly from the drum l2 through the down-comers 8| and up through the rear water wall tubes I9, which deliver a mixture of steam and water to the drum. Water also flows from the drum 2 through the down-comers H, and thence upwardly through tubes 55 and '14 to the front boiler drum Any steam formed in the tubes 55 and 14 is at once delivered into the main boiler circulation. The downeomers 16 supply the tubes 14 with any additional water which they may require.

It will now be seen that I have provided a simple and effective construction whereby all the heat exposed portions of an underfeed furnace may be effectively protected by the transfer of heat to water and the resulting generation of steam. The circulation of water through the various tubes is positive and unrestricted. All the heat exposed tubes slope upwardly in the direction of flow, so that the formation of steam pockets is avoided. The furnace can be operated for long periods at high combustion rates without danger of overheating its parts.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An underfeed furnace comprising a plurality of parallel underfeed retorts which are spaced apart to provide passages for air, means to feed fuel into the retorts, water tubes mounted above the air'passages and exposed on their upper surfaces to contact with the fuel bed, means to circulate water through the tubes, and tuyere members located close to and beneath the tubes and arranged to distribute air from said passages into the fuel.

"of parallel underfeed retorts which are spaced air from the passages upwardly between the tubes and laterally into the retorts.

3. An underfeed furnace comprising a plurality of parallel underfeed retorts which are spaced apart to provide passages for air, means to feed fuel into the front ends of the retorts, a pair of spaced parallel water tubes mounted above each air passage and sloping downwardly toward the rear, the tubes being exposed on their upper surfaces to contact with the fuel bed, means to circulate water through the tubes, and tuyere members located close to and beneath the tubes and arranged to direct jets of air upwardly and rearwardly between the tubes and laterally into the retorts.

4. An underfeed furnace comprising a plurality apart to provide passages for air, means to feed fuel into the front ends of the retorts, a pair of spaced parallel water tubes mounted above each air passage and sloping downwardly toward the rear, the tubes being exposed on their upper surfaces to contact with the fuel bed, means to circulate water through the tubes, and tuyere members located beneath the tubes and shaped to fit closely against the lower surfaces of the tubes, the tuyere members being shaped to provide tuyre openings leading laterally to the retorts and air passages which direct air upwardly between the tubes.

IRVING A. TAYLOR. 

